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Linking Explicitly

 

The latest version of this topic can be found at Linking Explicitly.

With explicit linking, applications must make a function call to explicitly load the DLL at run time. To explicitly link to a DLL, an application must:

  • Call LoadLibrary (or a similar function) to load the DLL and obtain a module handle.

  • Call GetProcAddress to obtain a function pointer to each exported function that the application wants to call. Because applications are calling the DLL's functions through a pointer, the compiler does not generate external references, so there is no need to link with an import library.

  • Call FreeLibrary when done with the DLL.

For example:

typedef UINT (CALLBACK* LPFNDLLFUNC1)(DWORD,UINT);  
...  
  
HINSTANCE hDLL;               // Handle to DLL  
LPFNDLLFUNC1 lpfnDllFunc1;    // Function pointer  
DWORD dwParam1;  
UINT  uParam2, uReturnVal;  
  
hDLL = LoadLibrary("MyDLL");  
if (hDLL != NULL)  
{  
   lpfnDllFunc1 = (LPFNDLLFUNC1)GetProcAddress(hDLL,  
                                           "DLLFunc1");  
   if (!lpfnDllFunc1)  
   {  
      // handle the error  
      FreeLibrary(hDLL);         
      return SOME_ERROR_CODE;  
   }  
   else  
   {  
      // call the function  
      uReturnVal = lpfnDllFunc1(dwParam1, uParam2);  
   }  
}  

Linking an Executable to a DLL

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